Great Optically Luminous Dropout Research Using Subaru HSC (GOLDRUSH). I. UV luminosity functions at z ∼ 4-7 derived with the half-million dropouts on the 100 deg <sup>2</sup> sky

Yoshiaki OnoMasami OuchiYuichi HarikaneJun ToshikawaMichael RauchSuraphong YumaMarcin SawickiTakatoshi ShibuyaKazuhiro ShimasakuMasamune OguriChris WillottMohammad AkhlaghiMasayuki AkiyamaJean CouponNobunari KashikawaYutaka KomiyamaAkira KonnoLihwai LinYoshiki MatsuokaSatoshi MiyazakiTohru NagaoKimihiko NakajimaJohn SilvermanMasayuki TanakaYoshiaki TaniguchiShiang Yu WangResearch Center for the Early UniverseAcademia Sinica, Institute of Astronomy and AstrophysicsNational Institutes of Natural Sciences - National Astronomical Observatory of JapanUniversity of TokyoEuropean Southern ObservatoryUniversité Claude Bernard Lyon 1The Graduate University for Advanced StudiesSaint Mary's UniversityThe Open University of JapanMahidol UniversityNational Research Council CanadaTohoku UniversityUniversité de GenèveCarnegie ObservatoriesEhime University2019-08-232019-08-232018-01-01Publications of the Astronomical Society of Japan. Vol.70, (2018)2053051X000462642-s2.0-85041660665https://repository.li.mahidol.ac.th/handle/20.500.14594/45752© The Author 2017. Published by Oxford University Press on behalf of the Astronomical Society of Japan. All rights reserved. We study the UV luminosity functions (LFs) at z ∼ 4, 5, 6, and 7 based on the deep largearea optical images taken by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP). On the 100 deg2 sky of the HSC SSP data available to date, we take enormous samples consisting of a total of 579565 dropout candidates at z ∼ 4-7 by the standard color selection technique, 358 out of which are spectroscopically confirmed by our followup spectroscopy and other studies. We obtain UV LFs at z ∼ 4-7 that span a very wide UV luminosity range of ∼0.002-100 L∗ UV (-26 < MUV < -14 mag) by combining LFs from our program and the ultra-deep Hubble Space Telescope legacy surveys.We derive three parameters of the best-fit Schechter function, φ∗, M∗ UV, and α, of the UV LFs in the magnitude range where the active galactic nucleus (AGN) contribution is negligible, and find that α and φ∗ decrease from z ∼ 4 to 7 with no significant evolution of M∗ UV . Because our HSC SSP data bridge the LFs of galaxies and AGNs with great statistical accuracy, we carefully investigate the bright end of the galaxy UV LFs that are estimated by the subtraction of the AGN contribution either aided by spectroscopy or the best-fit AGN UV LFs.We find that the bright end of the galaxy UV LFs cannot be explained by the Schechter function fits at>2 σ significance, and require either double power-law functions or modified Schechter functions that consider a magnification bias due to gravitational lensing.Mahidol UniversityEarth and Planetary SciencesPhysics and AstronomyGreat Optically Luminous Dropout Research Using Subaru HSC (GOLDRUSH). I. UV luminosity functions at z ∼ 4-7 derived with the half-million dropouts on the 100 deg <sup>2</sup> skyArticleSCOPUS10.1093/pasj/psx103